Analysis And Application Of Water Gushing History Of Typical Karst Mountain Tunnel In Southwest China

With the national "the Belt and Road" and "Ten Vertical and Ten Horizontal High-Speed Rail Net" planning continues to advance,in which transport projects occupy an irreplaceable role.However,the development of transport engineering is often subject to natural conditions factors,so the tunnel project came into being,especially in the southwest mountain area is the most common.In the southwest mountain tunnel project,groundwater disaster is very common.Due to the complexity and variability of geological conditions,the accidents of water burst and mud burst are often occurred in the process of tunnel excavation,which not only caused casualties and delays in the construction period,but also destroyed the tunnel area of groundwater environment.In the southwest mountainous area,a large number of karst aquifers are distributed,due to the inhomogeneity of karst development,the water burst accident of the tunnel is frequent and suddenly.Therefore,it is very important to study the gushing water problem of the southwest karst mountain tunnel.Many people have done a lot of research work on the problem of gushing water in karst tunnels.However,most of them have studied the total gushing water of tunnels,lacking systematic research of tunnel gushing course and summary rule of water burst.In this paper,typical mountain tunnel in southwest karst area is the research object.Based on the data of the dynamic curve(Q-T curve)of the gushing water of 17 tunnels,the characteristics of typical karst tunnel water burst process in southwest was analyzed and concluded,and further summarizes the water burst controlled factors,summed up the typical water burst geologic models.Finally,taking the construction of karst mountain tunnels in southwest as examples,combined with the quantitative analysis of numerical simulation and the actual monitoring data of the tunnel,the rationality of tunnel water gushing water curve and the geological model will be comprehensively demonstrated.At last,draw the following conclusions,which can play a great reference and research significance in the future engineering applications.1、Based on the example of the gushing process(Q-T curve)of 17 tunneling projects,from the tunnel gushing water direct supply source and the seepage channel between the gushing water source and the tunnel gushing point,divide the tunnel water gushing Q-T curve type.Among them,the water supply sources include rainfall,underground aquifer and mixed type.Connectivity of seepage channel is divided into cutthrough,owe through and gradually through.In the end,the Q-T curves of the tunnel gushing water are divided into seven types: rainfall recharge-rapid gushing type,rainfall recharge-slowly gushing type,underground water recharge-direct gushing type,underground water recharge-hysteresis type,mixed recharge-synchronization type,mixed recharge-hysteresis type,mixed recharge-mixed type.2 、 The Q-T curves of each type of tunnel water gushing have different characteristics,and analyzing their forming mechanism can induce and summarize the following factors: geological structure,karst development structure,hydrogeological condition,direct source of tunnel water gushing and tunnel correlation.3、Based on the analysis of the gushing process of the typical karst mountain tunnel in the southwest of China,the paper summarizes six common tunnel water gushing patterns in the southwestern China,namely: karst fissuring(fissuring)aquifer structure pattern,karst pipeline water structure pattern,the closed karst cavity water structure pattern,karst fissuring(fissuring)-karst pipeline water structure pattern,karst fissuring(fissuring)-karst cavity water structure pattern,fracture-karst pipeline water structure pattern.4、Taking the excavation section of Xie Ma tunnel in Chongqing as an example,the paper demonstrates the rationality of tunnel gushing geological model and controlled factors by numerical simulation and monitoring data.Based on the detailed analysis of the controlling factors of the gushing water in the tunnel area,it is concluded that the groundwater aquifer structure in the tunnel excavation section belongs to the karst fissuring(fissuring)-karst cavity water structure pattern and fracture-karst pipeline water structure pattern.Tunnel directly reveal the rich water soluble cavity and small underwater rivers.The main sources of the gushing water are water soluble cavity,shallow circulatory Da Lanchi-Wu Xiangmiao underground river and the karst fissure-dissolved hole aquifer.The correlation between tunnel water gushing and rainfall is poor.Finally,it is concluded that the Q-T curve of the gushing water in the excavation section of the Xie Ma tunnel belongs to the underground water recharge-direct gushing type.Based on the 3D simulation software Visual Modflow,simulate the tunneling section of water flood peak value is lagging behind the surface rainfall peak within 295 days.Based on the real time monitoring data of the incoming and outgoing water inflow of the tunnel,the tunnel water inflow reached the peak value after 4 to 6 months of rainfall.Therefore,the correlation between tunnel water gushing and rainfall is poor,and rainfall is not directly to the supplies.Combined with the tunnel gushing water directly to groundwater recharge,tunnel directly reveal the rich water soluble cavity and underground rivers.It is confirmed that the Q-T curve type of tunnel water gushing is the underground water recharge-direct gushing type.